We report cases of spotted fever rickettsiosis in Coronel Fabriciano Municipality of Minas Gerais State, Brazil. The cases occurred in May and June of 2000. During this period there were two deaths among children from an area named Pedreira in a periurban area of this municipality. In a boy who died with clinical manifestations of Brazilian spotted fever, a necropsy revealed the presence of a spotted fever group Rickettsia. The serological results confirm the difficulty in the differential diagnosis of patients with symptoms of rickettsial diseases.

The pathogenic rickettsiae are a group of obligately intracellular bacteria responsible for a variety of human diseases. Rickettsia rickettsii causes the rickettsial disease with the highest case fatality ratio currently in Brazil2 and is transmitted by the tick Amblyomma cajennense3. This disease called Brazilian spotted fever (BSF) was first described in Brazil by Piza as a disease equivalent to Rocky Mountain spotted fever in the United States4. In Brazil BSF is known to occur in the States of Minas Gerais, São Paulo, Rio de Janeiro, Espírito Santo and Bahia2. Rickettsia typhi associated with rats and fleas has also been described in several publications2. Recent data showing the presence of antibodies to Rickettsia felis in sera from patients with fever and rash in Brazil and R. felis DNA in the serum of one patient indicate that R. felis is a new Rickettsial disease in this Country5. We report cases of spotted fever rickettsiosis in Coronel Fabriciano Municipality in Minas Gerais State, Brazil.

MATERIAL AND METHODS

The cases occurred in May and June of 2000. Twenty one suspected cases presenting with fever and skin rash were notified in Coronel Fabriciano Municipality (Figure 1) during this period. The majority of the cases came from a periurban area with rural characteristics named Pedreira. Among these 21 suspected cases, two children (12 and 15 years) died. They were brothers who lived in the same house. The first one to become ill was 12 years old and during the course of his disease presented fever, nausea, vomiting, diarrhea, abdominal pain, headache, myalgia and edema. Terminally he developed renal failure and stupor. The second fatal case developed fever, rash, nausea, vomiting, diarrhea, abdominal pain, headache, myalgia, jaundice and renal failure. Both cases reported a tick bite.

The sera of 21 patients with fever and rash were tested by indirect immunofluorescence assay (IFA)1 for the presence of antibodies reactive with R. rickettsii, R. typhi and Ehrlichia chaffeensis. A necropsy was performed on the second fatal case with collection of tissue samples of skin, brain, stomach, liver, spleen, and kidneys. These materials were fixed in neutral-buffered formalin and shipped to the Rickettsial and Ehrlichial Diseases Research Laboratory, Department of Pathology, University of Texas Medical Branch (UTMB) at Galveston, USA. Immunohistochemical examination for spotted fever rickettsiae was performed as described previously6. DNA was extracted from the same material and evaluated by PCR amplification of the Rickettsia 17 kDa gene7.

RESULTS

Immunohistochemical evaluation of the necropsy materials utilizing an IgM monoclonal antibody against an LPS epitope specific for Rickettsia of the spotted fever group demonstrated intraendothelial rickettsiae in the second fatal case (patient JFM). PCR performed on the necropsy materials were not conclusive, presumably owing to the use of formalin, which damages DNA.

Among the suspected cases, four had antibodies to R. rickettsii by IFA with a titer of 1:64 (Table 1). None had antibodies to R. typhi, R. felis or E. chaffeensis as determined by IFA at a dilution of 1:64.

DISCUSSION

The serologic results demonstrated that it was possible to suspect a diagnosis of spotted fever rickettsiosis in only four cases. They were not capable of confirming spotted fever rickettsiosis or even of identifying the species of Rickettsia involved in these cases, as there is broad cross-reactivity between spotted fever group rickettsiae. Among these cases was that of a 15-year-old boy whose diagnosis of spotted fever rickettsiosis was confirmed by immunohistochemical tests on necropsy material.

These results demonstrate clearly the difficulty in the differential diagnosis among the various rickettsial diseases and between rickettsial diseases and other non-rickettsial diseases with fever and rash, such as dengue fever. The contribution of molecular biology and good surveillance can help to elucidate the microbial species of rickettsiae involved in many cases of unrecognized fever and deaths due to Rickettsia in Brazil.